1. Field of the Invention
The present invention relates to a color projector capable of producing a high-luminance projection optical image.
2. Description of the Related Art
Liquid-crystal projectors are widely used as color projectors. Color projectors of a variety of arrangements have been proposed in order to produce a bright projection image. In the invention described in Japanese laid-open patent application No. 62-59919, for example, a light from a light source is separated into lights of red, blue and green colors, and images of lights of respective colors, which are modulated by a light bulb comprised of three liquid-crystals or the like provided in response to lights of these colors, are synthesized by a cube prism or a dichroic prism. In this case, lights of red and blue colors are made incident on the reflection surface of 45xc2x0 of the cube prism as an S-polarized light and the other light of green color is made incident thereon as a P-polarized light, thereby improving a utilization factor of the light from the light source.
However, according to the above-mentioned arrangement, there are problems of axis alignment and position alignment for introducing the S-polarized light and the P-polarized light. Moreover, even when the color projector is arranged as described above, since lights of respective colors from the light source should be separated and lights of respective colors should be modulated by the light bulb, thereby resulting in images of lights of respective color being produced, a loss of light is large so that there is a limit in producing a bright projection image.
Moreover, according to this arrangement, a light source of a large output power is needed in order to increase a brightness. In this case, there arises a problem of heat generated from the light source. To solve this problem, a cooling means such as a powerful fan or the like is required so that a color projector is unavoidably made large in size.
As a color projector capable of producing a bright projection image, there is a color projector using a cathode-ray tube. In this case, the whole of the color projector becomes large in size. Also, since a high voltage is treated, there arise accompanying problems of considering safety or the like.
An object of the present invention is to provide a color projector in which the above-mentioned problems can be solved and a sufficiently bright color projection image can be produced, whereby the a color projector is miniaturized, avoids the handling of a high voltage and produces a homogeneous and excellent color projection image.
A color projector according to the present invention comprises plasma-discharge display devices for producing respective single color images of lights of red, green and blue, a synthesizing means for synthesizing respective single color images of lights of red, green and blue colors from these plasma-discharge display devices and a projection optical system for projecting a synthesized image from this synthesizing means.
That is, according to the present invention, images of light of red, green and blue colors of three primary colors for producing a color projection image are each directly obtained by a plasma-discharge display device whose luminance of light is high and which does not require the application of high voltage unlike a cathode-ray tube.